CN108141441B

CN108141441B - Multi-resolution decoding and modulating system

Info

Publication number: CN108141441B
Application number: CN201680055955.4A
Authority: CN
Inventors: R·马莫拉
Original assignee: Shure Acquisition Holdings Inc
Current assignee: Shure Acquisition Holdings Inc
Priority date: 2015-09-03
Filing date: 2016-09-02
Publication date: 2021-02-12
Anticipated expiration: 2036-09-02
Also published as: WO2017041000A1; US20170069333A1; EP3345369A1; TWI692752B; TW201711020A; US10134412B2; CN108141441A; EP3345369B1

Abstract

The present invention provides a multi-resolution coding and modulation system for maintaining audio continuity in a digital wireless audio system in harsh RF environments, including an audio codec coupled with a non-uniform layered modulation scheme that generates codewords having bits that differ in perceptual importance. When the wireless audio system is operating in a harsh RF environment, the RF SNR for decoding bits of high perceptual importance may be reduced while the RF SNR for decoding bits of low perceptual importance may be increased without adversely affecting the latency of the wireless audio system. Audio may be subjectively degraded rather than muted, which mitigates intermittent interference and multipath fading problems.

Description

Multi-resolution decoding and modulating system

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. patent application No. 14/844,678, filed on 3/9/2015, the contents of which are incorporated herein in their entirety.

Technical Field

The present application relates generally to a multi-resolution coding and modulation system. In particular, the present application relates to a multi-resolution coding and modulation system for preserving audio continuity in a digital wireless audio system and includes an audio codec coupled with a non-uniform layered modulation scheme that generates codewords having bits that differ in perceptual importance.

Background

Audio production may involve capturing, recording, and rendering sound of products such as television programs, news broadcasts, movies, live events, and other types of products using a number of components including microphones, wireless audio transmitters, wireless audio receivers, recorders, and/or mixers. The microphone typically captures sound of the product that is wirelessly transmitted from the microphone and/or wireless audio transmitter to the wireless audio receiver. A wireless audio receiver may be connected to the recorder and/or mixer to record and/or mix sound by a member of the group, such as a product sound mixer. Electronic devices such as computers and smart phones may be connected to the recorder and/or mixer to allow panelist members to monitor the audio level and time code.

Wireless audio transmitters, wireless audio receivers, wireless microphones, and other portable wireless communication devices include antennas for transmitting Radio Frequency (RF) signals containing digital or analog signals, such as modulated audio signals, data signals, and/or control signals. Users of portable wireless communication devices include stage performers, singers, actors, newsreaders, and the like.

The wireless audio transmitter may transmit an RF signal including an audio signal to the wireless audio receiver. The wireless audio transmitter may be included, for example, in a wireless handheld microphone held by a user and including an integrated transmitter and antenna. When an RF signal is received at a wireless audio receiver, the RF signal may be degraded due to multipath fading caused by constructive interference and/or other types of interference. This degradation may cause the RF signal to have a poor signal-to-noise ratio (SNR), which may result in bit errors, which may cause artificial audio (audio artifacts). Typically, when significant artificial audio is present, the output audio is muted. However, in many scenarios and environments, it is undesirable to mute the output audio. The effects of such multipath fading and interference are most prevalent in harsh RF environments where physical and electrical factors (e.g., movement of microphones within the environment, other RF signals, etc.) affect the transmission and reception of RF signals. Furthermore, wireless audio systems typically utilize Forward Error Correction (FEC) in a homogeneous manner to account for errors in wireless transmissions, i.e., where the number of added bits is equal to the number of data bits, regardless of the perceptual importance of the data bits. This approach effectively wastes spectral bandwidth.

Thus, there is an opportunity for a multi-resolution decoding and modulation system that addresses these issues. More particularly, there is an opportunity for a multi-resolution coding and modulation system that preserves audio continuity in digital wireless audio systems in harsh RF environments by subjectively degrading the audio rather than muting the audio.

Disclosure of Invention

The present invention intends to solve the above mentioned problems by providing a multi-resolution coding and modulation system and method designed to, among others: (1) utilizing an audio codec coupled with a non-uniform layered modulation scheme in a wireless audio system, the audio codec producing codewords having bits that differ in perceptual importance; (2) reducing the RF SNR for decoding bits of high perceptual importance; (3) increasing the RF SNR for decoding bits with low perceptual importance; and (4) no adverse effect on the delay of the wireless audio system.

In an embodiment, a method of communicating an audio signal represented by a digital audio bitstream may comprise: encoding the digital audio bitstream into coarse codeword bits and fine codeword bits, wherein the coarse codeword bits represent high perceptual importance of the audio signal and the fine codeword bits represent low perceptual importance of the audio signal; selecting symbols of a complex constellation associated with a non-uniform hierarchical digital modulation scheme based on the coarse codeword bits and the fine codeword bits; modulating the symbols into Radio Frequency (RF) signals; transmitting the RF signal on a transmit antenna; receiving the RF signal on a receive antenna; sampling the received RF signal into a received digital signal; and detecting received symbols of a complex symbol stream in the received digital signal as bits designating a received quadrant and a received point. If both the bits specifying the received quadrant and the bits specifying the received point are detected, the method may also include decoding the received symbol into received coarse codeword bits and received fine codeword bits based on the received quadrant and the received point; and generating an output digital audio signal based on the received coarse codeword bits and the received fine codeword bits. However, if only the bits specifying the received quadrant are detected, the method may include decoding the received symbol into the received coarse codeword bits based on the received quadrant; and generating the output digital audio signal based on the received coarse codeword bits. If the bit designating the received quadrant or the bit designating the received point is not detected without error, the method may include generating audio silence for the output digital audio signal.

In another embodiment, a wireless audio system may include a transmitter having a transmitter audio codec, a multi-resolution mapper, a modulator, and a transmit antenna. The transmitter audio codec may be configured to receive a digital audio bitstream representative of an audio signal and encode the digital audio bitstream into coarse codeword bits and fine codeword bits, wherein the coarse codeword bits represent high perceptual importance of the audio signal and the fine codeword bits represent low perceptual importance of the audio signal. The multi-resolution mapper may be in communication with the transmitter audio codec and configured to select symbols of a complex constellation associated with a non-uniform hierarchical digital modulation scheme based on the coarse codeword bits and the fine codeword bits. The modulator may be in communication with the multi-resolution mapper and configured to modulate the symbols into a Radio Frequency (RF) signal, and the transmit antenna may be in communication with the modulator and configured to transmit the RF signal.

The wireless audio system may also include a receiver having a receive antenna, an analog-to-digital converter (ADC), a detector, a multi-resolution decoder, and a receiver audio codec. The receive antenna may be configured to receive the RF signal, and the ADC may be configured to sample the received RF signal into a received digital signal. The detector may be in communication with the receive antenna and configured to detect received symbols of a complex symbol stream in the received digital signal as bits specifying a received quadrant and a received point. The multi-resolution decoder may be in communication with the detector and configured to, if both the bits specifying the received quadrant and the bits specifying the received point are detected, decode the received symbol into received coarse codeword bits and received fine codeword bits based on the received quadrant and the received point; decoding the received symbol into the received coarse codeword bits based on the received quadrant if only the bits specifying the received quadrant are detected; and generating an audio mute if the bit designating the received quadrant or the bit designating the received point is not detected. The receiver audio codec may be in communication with the multi-resolution decoder and configured to generate an output digital audio signal based on the received coarse codeword bits and the received fine codeword bits if both the bits specifying the received quadrant and the bits specifying the received point are detected; generating the output digital audio signal based on the received coarse codeword bits if only the bits specifying the received quadrant are detected; and if the bit designating the received quadrant or the bit designating the received point is not detected, generating the output digital audio signal with the audio silence.

These and other embodiments and various arrangements and aspects will be apparent from and more fully understood from the following detailed description and accompanying drawings which set forth illustrative embodiments, indicative of the various ways in which the principles of the invention may be employed.

Drawings

Fig. 1 is a block diagram of a wireless audio system including a multi-resolution coding and modulation system used in conjunction with an RF transmitter and RF receiver, according to some embodiments.

Fig. 2 is a flow diagram illustrating operations for communicating an audio signal represented by a digital audio bitstream using a multi-resolution coding and modulation system in conjunction with an RF transmitter and an RF receiver, according to some embodiments.

Fig. 3 is a flow diagram illustrating operations for detecting received symbols of a constellation diagram from received digital signals, in accordance with some embodiments.

Fig. 4 is an illustration of an exemplary constellation diagram associated with a non-uniform hierarchical digital modulation scheme, in accordance with some embodiments.

Fig. 5 is an exemplary graph showing performance of a conventional wireless audio system.

Fig. 6 is an exemplary graph showing performance of a wireless audio system including a multi-resolution coding and modulation system.

Fig. 7 is a block diagram of a wireless audio system including a multi-resolution coding and modulation system with forward error correction used in conjunction with an RF transmitter and an RF receiver, according to some embodiments.

Detailed Description

The following detailed description describes, illustrates, and exemplifies one or more specific embodiments of the present invention according to the principles of the present invention. This detailed description is not provided to limit the disclosure to the embodiments described herein, but rather to explain and teach the principles of the disclosure so that one of ordinary skill in the art can understand these principles and, based thereon, can apply the principles to practice not only the embodiments described herein, but other embodiments as may be conceived in accordance with these principles. The scope of the invention is intended to cover all such embodiments that may fall within the scope of the appended claims either literally or under the doctrine of equivalents.

It should be noted that in the detailed description and the accompanying drawings, similar or substantially similar elements may be labeled with the same element numbers. However, these elements may sometimes be labeled with different numbers, such as, for example, where such labeling facilitates a clearer description. Additionally, the drawings set forth herein are not necessarily drawn to scale and, in some instances, the proportions may have been exaggerated to more clearly depict certain features. Such labeling and drawing practices do not necessarily imply a potentially substantial purpose. As set forth above, the present specification is intended to be considered as a whole and to be construed in accordance with the principles of the invention as taught herein and understood by those of ordinary skill in the art.

The multi-resolution coding and modulation systems described herein may be utilized in wireless audio systems with RF transmitters and RF receivers to maintain audio continuity by reducing the RF SNR for decoding bits of high perceptual importance and increasing the RF SNR for decoding bits of low perceptual importance, while delaying the delay for wireless audio systems

Has no adverse effect. An audio codec that generates codewords with bits that differ in perceptual importance may be coupled with a non-uniform layered modulation scheme in a multi-resolution coding and modulation system. By subjectively degrading audio in harsh RF environments, rather than muting the audio as in conventional wireless audio systems, multi-resolution coding and modulation systems may help mitigate intermittent interference and multipath fading issues. In addition, multi-resolution coding and modulation systems may improve spectral efficiency and have an extended operating range in a non-fading environment.

As an example of varying the benefits of RF SNR for decoding bits of different perceptual importance, fig. 5 depicts an exemplary graph showing the performance of a conventional wireless audio system without the benefits of the multi-resolution coding and modulation systems described herein. In fig. 5, the SNR of the received RF signal on the y-axis is plotted against time on the x-axis. As shown in fig. 5, conventional wireless audio systems have a critical RF SNR such that when the SNR of the received RF signal is below the critical RF SNR, audio loss (i.e., muting) in the output audio may occur due to a failure to successfully decode the audio.

In contrast, fig. 6 depicts an exemplary graph showing performance of a wireless audio system including the multi-resolution coding and modulation system described herein. In fig. 6, the SNR of the received RF signal on the y-axis is plotted against time on the x-axis. The critical RF SNR for a conventional wireless audio system and the critical RF SNR for a wireless audio system including a multi-resolution coding and modulation system are shown in fig. 6. As can be seen in fig. 6, by reducing the critical RF SNR for perceptually important audio, audio loss (muting) can be avoided in this audio because the output audio can be successfully decoded. In addition, fig. 6 shows the affected RF SNR for a wireless audio system including a multi-resolution coding and modulation system, which represents a case where audio can be affected in an insignificant manner, for example, by limiting the decoded audio band to 0-12 kHz instead of a wider range in some embodiments. Audio in the range of 0 to 12kHz, for example, may be considered perceptually important audio, while audio in higher frequency ranges may be considered perceptually less important. In other embodiments, the audio may be affected in an insignificant manner by reducing the SNR of the audio. The multi-resolution coding and modulation system may be configured such that the higher RF SNR threshold is within the attenuation margin of the link between the transmitter and the receiver. Thus, wireless systems will typically operate in a regime where full fidelity audio is present.

Fig. 1 is an exemplary block diagram of a wireless audio system 100 including a multi-resolution coding and modulation system. The wireless audio system 100 may include an RF transmitter 102 that transmits an RF signal containing an audio signal from an audio source 104. In some embodiments, the RF transmitter 102 may be integrated within a handheld microphone. The transmitted RF signal may be received by an RF receiver 152 that processes the RF signal to generate an output analog audio signal 166. In some embodiments, the RF receiver 152 may generate an output digital audio signal. In some embodiments, the RF receiver may be a rack-mounted unit, a portable unit, and/or a camera-mounted unit. A process 200 that may use the wireless audio system 100 is shown in fig. 2. In particular, the wireless audio system 100 and process 200 may utilize a multi-resolution coding and modulation system to ensure continuity of wirelessly transmitted audio. The various components included in the wireless audio system 100 may be implemented using software executable by one or more servers or computers, such as computing devices having processors and memories, and/or implemented by hardware, such as discrete logic circuits, Application Specific Integrated Circuits (ASICs), Programmable Gate Arrays (PGAs), Field Programmable Gate Arrays (FPGAs), etc.

An audio source 104, such as a microphone or playback device, may detect and/or generate an audio signal. For example, if the audio source is a microphone, sound may be detected and converted into an audio signal. The audio source 104 may generate an analog audio signal that is modulated and transmitted by the RF transmitter 102. The analog audio signal from the audio source 104 may be converted to a digital audio bit stream by an analog-to-digital converter (ADC) 106.

For example, at step 204 of the process 200 shown in fig. 2, the audio codec 108 may receive a digital audio bitstream and generate codewords having bits that differ in perceptual importance of the audio signal. In an embodiment, a multi-resolution coding and modulation system may prioritize the bits of codewords that encode the perceptually important frequency ranges of audio. A typical frequency range for human hearing may be from about 0 to 24 kHz. However, certain frequency ranges may be considered to be of higher perceptual importance than other frequency ranges. For example, codeword bits corresponding to audio in a frequency range of 0 to 12kHz may be assigned to be of high perceptual importance. Codeword bits representing audio in another frequency range, such as 12-24 kHz, may be assigned to have low perceptual importance. In this example, audio having frequencies greater than 12kHz may be considered less important because such audio is generally harder to hear. As another example, codeword bits corresponding to audio in a frequency range of 0 to 6kHz may be assigned to have high perceptual importance, while codeword bits representing audio in another frequency range, such as 6 to 12kHz, may be assigned to have low perceptual importance. In this example, audio having frequencies greater than 6kHz may be considered less important. Other frequency ranges for determining the perceptual importance of audio are possible and contemplated.

In other embodiments, the multi-resolution coding and modulation system may prioritize the bits of the codeword that correctly transmit will result in a perceptually acceptable (but reduced) audio SNR. In other words, if only perceptually important bits of a codeword can be decoded, there may be a reduction in audio SNR as compared to the case where all bits of the codeword can be successfully decoded. For example, in an 8-bit codeword, the four most significant bits can achieve an audio SNR of 24dB and these bits will be considered perceptually important. In this example, assuming four perceptually important bits were successfully transmitted, the four least significant bits of the codeword may represent an additional 24dB of audio SNR. In this case, the four least significant bits may be considered less significant because the audio SNR of the first 24dB is more relevant compared to the order perception from 24dB to 48 dB.

Thus, for example, at step 204 of the process 200 shown in fig. 2, the audio codec 108 may encode the digital audio bitstream into a codeword having coarse bits and fine bits based on the perceptual importance of the audio. The coarse codeword bits may represent audio having a high perceptual importance deemed to be more important. Thus, the audio codec 108 may generate coarse codeword bits for this type of audio. The fine codeword bits may represent audio having a low perceptual importance that is deemed less important. Thus, the audio codec 108 may generate fine codeword bits for this type of audio.

For example, at step 206 of the process 200 shown in fig. 2, the coarse codeword bits and the fine codeword bits generated by the audio codec 108 may be utilized by the multi-resolution mapper 110 in the RF transmitter 102 to select quadrants and points (i.e., symbols) of the constellation associated with the non-uniform hierarchical digital modulation scheme. The hierarchical digital modulation scheme may include 16-Quadrature Amplitude Modulation (QAM), 32-QAM, M-Phase Shift Keying (PSK), and/or other suitable linear modulation schemes. An exemplary constellation diagram associated with the 16-QAM modulation scheme is depicted in fig. 4. The star diagram of fig. 4 illustrates how a signal may be modulated by a 16-QAM modulation scheme in the complex plane (having in-phase (I) and quadrature (Q) axes), and includes four quadrants 402 and sixteen points (each depicted by an "X"). There are four points in each quadrant 402.

The distance between the points and/or the density of the points may be configured by a parameter λ. The parameter λ may be set based on the particular environment and/or application in which the wireless audio system 100 is used. In an embodiment, the parameter λ is based on the distance between quadrants (coarse) and points (fine) in a constellation diagram scaled to have unit Root Mean Square (RMS) power. In particular, the parameter λ may be equal to a minimum Euclidean distance (D) between points₁) Divided by the minimum Euclidean distance (D) between quadrants₂). An exemplary distance D is shown in the constellation diagram illustration of FIG. 4₁And D₂. Other ways of parameterizing the heterogeneous hierarchical star map may be utilized in other embodiments.

The multi-resolution mapper 110 may select one of the quadrants 402 based on the coarse codeword bits received from the audio codec 108 and one of the points based on the fine codeword bits received from the audio codec 108. For example, a codeword that includes coarse codeword bits and fine codeword bits from the audio codec 108 may be 16 bits. Eight bits of the codeword may correspond to coarse bits (i.e., of higher perceptual importance) and the other eight bits may correspond to fine bits (i.e., of lower perceptual importance). In the case where the hierarchical digital modulation scheme is 16-QAM, each point may have quadrant (coarse) information of two bits and point (fine) information of two bits. Thus, an exemplary codeword of 16 bits would include information mapped to four points (symbols) of a 16-QAM constellation.

In some embodiments, the coarse codeword bits and the fine codeword bits generated by the audio codec 108 may be encoded using a Forward Error Correction (FEC) code, as is known in the art. The use of FEC enables the correction of some bit errors caused by noise and interference in the received signal. Fig. 7 is an exemplary block diagram of a wireless audio system 700, the wireless audio system 700 including a multi-resolution coding and modulation system with an FEC encoder 709 in a transmitter 702 and an FEC decoder 761 in a receiver 752. Other components of the wireless audio system 700 are the same as described with respect to fig. 1. The coarse codeword bits and the fine codeword bits from the audio codec 108 may be encoded by separate FEC encoders 709 in the transmitter 702 corresponding to the high perceptual importance audio and the low perceptual importance audio, respectively. After encoding using FEC, the FEC-encoded coarse and fine codeword bits may be utilized by the multi-resolution mapper 110 to select quadrants and points (i.e., symbols) of the constellation diagram, as described above.

For example, at step 208 of the process 200, the modulator 112 may utilize the selected quadrants and points from the multi-resolution mapper 110 to modulate the digital audio bitstream into a modulated signal. The digital audio bit stream is modulated according to the particular hierarchical digital modulation scheme utilized, e.g., 16-QAM. In particular, the I and Q signals corresponding to the selected quadrant and selected point (i.e., symbol) are pulse-shaped to generate a modulated signal, as is known in the art. The modulated signal from modulator 112 may be converted to an analog format by digital-to-analog converter (DAC)114 and then transmitted in RF over transmit antenna 116, e.g., at step 210 of process 200.

For example, at step 212 of process 200, an RF signal may be received at RF receiver 152 from transmit antenna 116 by receive antenna 154. The received RF signal may be sampled and converted to a received digital signal by the ADC 156, for example, at step 213 of the process 200. As is known in the art, the detector 158 may detect the received symbol as specified by the (I, Q) coordinates in the complex plane, for example, at step 214 of the process 200. This symbol should correspond to the constellation diagram associated with the hierarchical digital modulation scheme utilized. Under ideal conditions, both the quadrant and point of each symbol in the received digital signal will exactly match the quadrant and point in the transmitted signal. However, due to multipath fading and other types of interference, the received digital signal may have degraded such that the quadrants and/or points may not be identical to the quadrants and/or points in the transmitted signal. The received symbols may be provided from the detector 158 to a multi-resolution decoder 160 in the RF receiver 152. If nothing is detected, the detector 158 may also not provide anything to the multi-resolution decoder 160. The details of how the detector 158 can detect and determine the received symbols in the received digital signal (containing the digital symbol stream) and how the multi-resolution decoder 160 can decode the digital symbol stream are described with reference to the process depicted in fig. 3.

For example, at step 302 of process 214 shown in fig. 3, detector 158 may determine quadrants and points (i.e., symbols) from the received digital signals. Quadrants and points may be detected in the received digital signal, but as previously described, such quadrants and/or points may not exactly match quadrants and/or points in the transmitted signal. The multi-resolution decoder 160 may decode quadrant (coarse) bits and point (fine) bits from the received digital symbol stream. In particular, the multi-resolution decoder 160 may receive a particular point (symbol) and blindly decode quadrant (coarse) bits based on the quadrant in which the received point is located. Error detection like both bit-limit and point-location may be performed by the multi-resolution decoder 160 to ensure that correct information has been received. In some embodiments, a Cyclic Redundancy Check (CRC) scheme may be utilized, as is known in the art. In other embodiments, a Soft Decoding scheme may be utilized, such as described in the concurrently filed and commonly owned patent application "Soft Decision Audio Decoding System" (attorney docket No. 025087-.

For example, at step 304 of process 214, error detection of the point bits may be performed. If the error detection for the point location passes, multi-resolution decoder 160 may specify that the received point was detected, e.g., at step 306 of process 214. However, if the error detection of the point location fails, multi-resolution decoder 160 may specify that the received point was not detected, e.g., at step 308 of process 214. Next, at step 310 of process 214, the multi-resolution decoder 160 may perform error detection of object bounds. If the false detection of the object limit passes, then the multi-resolution decoder 160 may designate that the received quadrant was detected, for example, at step 312 of process 214. However, if the false detection of the object limit fails, then the multi-resolution decoder 160 may specify that the received quadrant was not detected, for example, at step 314 of process 214. If process 214 determines that both the received quadrant and the received point have been detected, both the received quadrant and the received point may be utilized to recover the audio. However, if process 214 determines that only the received quadrant has been detected, then only the received quadrant may be utilized to restore audio. And, if process 214 determines that both the received quadrant and the received point are not detected, audio silence may be generated in the output audio.

Returning to process 200 of fig. 2, multi-resolution decoder 160 may then determine whether both the received quadrant and the received point have been detected, whether only the received quadrant has been detected, or whether nothing has been detected, such as at step 216 of process 200. If both the received quadrant and the received point have been detected at step 216, the multi-resolution decoder 160 may decode the received digital symbols into coarse codeword bits and fine codeword bits based on the received quadrant and the received point, such as at step 218 of process 200. In this case, the audio codec 162 in the RF receiver 152 may receive the coarse codeword bits and the fine codeword bits from the multiresolution decoder 160 and generate an output digital audio signal based on the coarse codeword bits and the fine codeword bits, such as at step 220 of the process 200.

However, if only the received quadrant has been detected at step 216, then the multi-resolution decoder 160 may decode the received digital symbols into coarse codeword bits based on the received quadrant, such as at step 222 of process 200. In this case, audio codec 162 may receive the coarse codeword bits from multi-resolution decoder 160 and generate an output digital audio signal based only on the coarse codeword bits, such as at step 224 of process 200. If both the received quadrant and the received point have not been detected at step 216, multi-resolution decoder 160 and audio codec 162 may generate audio muting, such as at step 226 of process 200. In some embodiments, the output digital audio signal from the audio codec 162 may be converted to an output analog audio signal 166 by the DAC 164. The output analog audio signal 166 can be utilized as desired, such as for further processing by downstream devices (e.g., mixers, recorders, etc.), playing on a speaker, and so forth.

In some embodiments in which the coarse codeword bits and the fine codeword bits have been encoded using FEC in the transmitter (as described above), the FEC decoder 761 may decode the coarse codeword bits and the fine codeword bits from the multi-resolution decoder 160, as shown in fig. 7. The coarse codeword bits and the fine codeword bits may be decoded by separate FEC decoders 761 in the receiver 752, corresponding to the high perceptual importance audio and the low perceptual importance audio, respectively. After FEC decoding, the decoded coarse codeword bits and fine codeword bits may be utilized by audio codec 162 to generate an output digital audio signal and/or an output analog audio signal, as described above.

It will be understood by those of ordinary skill in the art that any process descriptions or blocks in the figures should be understood as representing modules, segments, or portions of code which include one or more executable instructions for implementing specific logical functions or steps in the process, and alternate implementations are included within the scope of the embodiments of the present invention in which functions may be executed out of order from that shown or discussed, including substantially concurrently or in reverse order, depending on the functionality involved.

It is intended to explain how to fashion and use various embodiments in accordance with the technology rather than to limit the true, intended, and fair scope and spirit thereof. The foregoing description is not intended to be exhaustive or to be limited to the precise form disclosed. Modifications or variations are possible in light of the above teachings. The embodiments were chosen and described to provide the best illustration of the principles of the described technology and its practical application, and to enable one of ordinary skill in the art to utilize the technology in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the embodiments as determined by the appended claims, as may be amended during the pendency of this application for patent, and all equivalents thereof, when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

Claims

1. A method of communicating an audio signal represented by a digital audio bitstream, comprising:

encoding the digital audio bitstream into coarse codeword bits and fine codeword bits, wherein the coarse codeword bits represent high auditory perceptual importance of the audio signal and the fine codeword bits represent low auditory perceptual importance of the audio signal;

selecting symbols of a complex constellation associated with a non-uniform hierarchical digital modulation scheme based on the coarse codeword bits and the fine codeword bits;

modulating the symbols into Radio Frequency (RF) signals;

transmitting the RF signal on a transmit antenna;

receiving the RF signal on a receive antenna;

sampling the received RF signal into a received digital signal;

detecting received symbols of a complex symbol stream in the received digital signal as bits specifying a received quadrant and a received point;

if both the bit specifying the received quadrant and the bit specifying the received point are detected:

decoding the received symbol into received coarse codeword bits and received fine codeword bits based on the received quadrant and the received point; and is

Generating an output digital audio signal based on the received coarse codeword bits and the received fine codeword bits;

if only the bit designating the received quadrant is detected, then:

decoding the received symbol into the received coarse codeword bits based on the received quadrant; and is

Generating the output digital audio signal based on the received coarse codeword bits; and

generating audio silence for the output digital audio signal if the bit designating the received quadrant or the bit designating the received point is not detected without error.

2. The method of claim 1, wherein encoding the digital audio bitstream comprises:

designating the coarse codeword bits as representing the audio signal of the high auditory perceptual importance in a perceptually important frequency range; and

designating the fine codeword bits as representing the audio signal having the low auditory perceptual importance in a perceptually less important frequency range.

3. The method of claim 2, wherein:

the perceptually important frequency range is from about 0kHz to about 12 kHz; and is

The perceptually less important frequency range is from about 12kHz to about 24 kHz.

4. The method of claim 1, wherein encoding the digital audio bitstream comprises:

designating the coarse codeword bits as representing the audio signal having a minimum perceptually acceptable signal-to-noise ratio, SNR; and

designating the fine codeword bits as representing the audio signal having an SNR that exceeds the minimum perceptually acceptable SNR established by the coarse codeword bits.

5. The method of claim 1, wherein the hierarchical digital modulation scheme comprises 16-Quadrature Amplitude Modulation (QAM).

6. The method of claim 1, wherein the minimum euclidean distance D between points equal to the constellation diagram may be based on₁Divided by the minimum Euclidean distance D between the quadrants of the constellation diagram₂Configures the distances between the points of the constellation diagram associated with the hierarchical digital modulation scheme.

7. The method of claim 1, wherein detecting the received symbol comprises:

determining the received quadrant and the received point from the received digital signal;

performing error detection on the bits specifying the received point;

designating the received point as detected from the received digital signal if the error detection on the bit designating the received point passes;

designating the received point as not detected from the received digital signal if the error detection on the bit designating the received point fails;

performing error detection on the bits specifying the received quadrant;

designating the received quadrant as detected from the received digital signal if the error detection on the bit designating the received quadrant passes; and

designating the received quadrant as not detected from the received digital signal if the error detection for the bit designating the received quadrant fails.

8. The method of claim 1:

further comprising encoding the coarse codeword bits and the fine codeword bits using a forward error correction, FEC, code;

wherein detecting the received symbol comprises:

decoding the received symbols encoded using the FEC code;

determining the received quadrant and the received point from the FEC decoded received symbols;

performing error detection on the bits specifying the received point;

designating the received dot as detected if the error detection on the bit designating the received dot passes;

performing error detection on the bits specifying the received quadrant;

designating the received quadrant as not detected from the received digital signal if the error detection on the bit designating the received quadrant fails;

wherein selecting the symbol comprises selecting the symbol based on the FEC encoded coarse codeword bits and the FEC encoded fine codeword bits.

9. A wireless audio system, comprising:

(A) a transmitter, comprising:

(1) a transmitter audio codec configured to:

receiving a digital audio bit stream representing an audio signal; and is

(2) a multi-resolution mapper in communication with the transmitter audio codec, the multi-resolution mapper configured to select symbols of a complex constellation associated with a non-uniform hierarchical digital modulation scheme based on the coarse codeword bits and the fine codeword bits;

(3) a modulator in communication with the multi-resolution mapper, the modulator configured to modulate the symbols into Radio Frequency (RF) signals; and

(4) a transmit antenna in communication with the modulator, the transmit antenna configured to transmit the RF signal; and

(B) a receiver, comprising:

(1) a receive antenna configured to receive the RF signal;

(2) an analog-to-digital converter configured to sample the received RF signal into a received digital signal;

(3) a detector in communication with the receive antenna, the detector configured to detect received symbols of a complex symbol stream in the received digital signal as bits specifying a received quadrant and a received point;

(4) a multi-resolution decoder in communication with the detector, the multi-resolution decoder configured to:

decoding the received symbol into received coarse codeword bits and received fine codeword bits based on the received quadrant and the received point if both the bits specifying the received quadrant and the bits specifying the received point are detected;

decoding the received symbol into the received coarse codeword bits based on the received quadrant if only the bits specifying the received quadrant are detected; and is

Generating an audio mute if the bit designating the received quadrant or the bit designating the received point is not detected; and

(5) a receiver audio codec in communication with the multi-resolution decoder, the receiver audio codec configured to:

generating an output digital audio signal based on the received coarse codeword bits and the received fine codeword bits if both the bits specifying the received quadrant and the bits specifying the received point are detected;

generating the output digital audio signal based on the received coarse codeword bits if only the bits specifying the received quadrant are detected; and is

Generating the output digital audio signal with the audio silence if the bit designating the received quadrant or the bit designating the received point is not detected.

10. The wireless audio system of claim 9, wherein the transmitter audio codec is configured to encode the digital audio bitstream by:

11. The wireless audio system of claim 10, wherein:

12. The wireless audio system of claim 9, wherein the transmitter audio codec is configured to encode the digital audio bitstream by:

13. The wireless audio system of claim 9, wherein the layered digital modulation scheme comprises 16-Quadrature Amplitude Modulation (QAM).

14. The wireless audio system of claim 9, wherein the minimum euclidean distance D between points equaling the constellation diagram may be based on₁Divided by the minimum Euclidean distance D between the quadrants of the constellation diagram₂Configures the distances between the points of the constellation diagram associated with the hierarchical digital modulation scheme.

15. The wireless audio system of claim 9, wherein the detector is configured to detect the received symbol by:

performing error detection on the bits specifying the received point;

performing error detection on the bits specifying the received quadrant;

16. The wireless audio system of claim 9:

it further comprises:

a first Forward Error Correction (FEC) encoder in communication with the transmitter audio codec and the multi-resolution mapper, the first FEC encoder configured to encode the coarse codeword bits using an FEC code;

a second FEC encoder in communication with the transmitter audio codec and the multi-resolution mapper, the second FEC encoder configured to encode the fine codeword bits using the FEC code;

a first FEC decoder in communication with the multi-resolution decoder and the receiver audio codec, the first FEC decoder configured to decode the received symbols encoded using the FEC code; and

a second FEC decoder in communication with the multi-resolution decoder and the receiver audio codec, the second FEC decoder configured to decode the received symbols encoded using the FEC code;

wherein the detector is configured to detect the received symbol by:

performing error detection on the bits specifying the received point;

performing error detection on the bits specifying the received quadrant;

wherein the multi-resolution mapper is configured to select the symbol by selecting the symbol based on the FEC encoded coarse codeword bits and the FEC encoded fine codeword bits.

17. The wireless audio system of claim 9, wherein:

the transmitter further comprises a first analog-to-digital converter in communication with the transmitter audio codec and an audio source providing the audio signal, the first analog-to-digital converter configured to convert the audio signal into the digital audio bitstream;

the modulator comprises a first digital-to-analog converter in communication with the modulator and the transmit antenna, the first digital-to-analog converter configured to convert the modulated symbols to the RF signal; and is

The receiver further includes a second digital-to-analog converter in communication with the receiver audio codec, the second digital-to-analog converter configured to convert the output digital audio signal to an output analog audio signal.